I won't cop to how many times in my career, a frustrating problem turned out to be something like accidentally hitting a record inhibit setting on a deck, or not noticing that it was in composite input instead of SDI.

I think your problem is pilot error but you have built up a perceptual blind spot as to what it is, because it is too obvious, and your impatient brain is skipping over what your eye is telling you. I know that's often the case when I make a mistake.

Changing perspective or order of operations might help. Run your checklist of tasks out loud and physically put your finger on every button, every menu setting, say it out loud, don't just assume it. "It's supposed to say THIS; does it indeed say that?"